1. Field of the Invention
This invention relates to a GPS (Global Positioning System) receiver and a GPS receiver system including a pair of GPS receivers that enables acquisition of not only positioning information but also azimuth information.
2. Description of the Prior Art
Previously, the conventional GPS receiver, which was equipped with an antenna unit having a substantially hemispherical antenna pattern, a receiver unit and a result output unit, was able to utilize signals transmitted by multiple GPS satellites to acquire such positioning information as latitude, longitude, altitude and GPS time but was incapable of acquiring azimuth information.
The inventor therefore developed a method for acquiring azimuth information by use of a pair of planar patch antennas (U.S. Ser. No. 09/818,844 and Japanese Patent Application Nos. 2000-91362 and 2001-93964).
This method for acquiring azimuth information includes a step of disposing a pair of planar patch antennas back-to-back, parallel to each other and vertical, whereby each planar patch antenna forms a sky coverage area of antenna sensitivity that is a sky quarter-sphere in the direction the antenna faces; a step of causing receiver units connected to the respective antennas to extract strength values of all received GPS satellite signals; a step of discriminating based on a comparison of the extracted signal strength values the antenna in whose sky coverage area the GPS satellite that transmitted each signal is present; a stop of arranging the results of the step of discriminating areas of satellite presence in a ring-like sequence; and a step of determining or limiting an azimuth of a measurement direction based on information contained in a ring-like discrimination results sequence.
Thus, in order to acquire azimuth information, it is necessary to compare the strength values of multiple satellite signals received by two GPS receivers and to discriminate the antenna in whose sky coverage area each GPS satellite is present. Since conventional GPS receivers are not capable of exchanging information with each other or of calculating azimuth information based on exchanged information, however, it has not been possible to acquire azimuth information even by disposing a pair of GPS receivers with their patch antennas disposed back-to-back, parallel to each other and vertical.
The present invention was accomplished in light of the foregoing circumstances and has as an object to provide a GPS receiver and a GPS receiver system including a pair of GPS receivers that enables acquisition of not only positioning information as heretofore but also azimuth information.
The invention achieves this object by providing a GPS receiver including an antenna unit, a GPS receiver unit and a result output unit, the GPS receiver comprising; a data transmitting unit, a data receiving unit, a data processing unit for carrying out calculation on data containing a strength value of each received GPS satellite signal to limit or determine an azimuth of a measurement direction, and a use mode control switch.
The data transmitting unit incorporates an infrared transmit facility, the data receiving unit incorporates an infrared receive facility, and the data transmitting unit and the data receiving unit are installed symmetrically with respect to a center point of their installation surface. Thus when two GPS receivers are placed in opposite vertical orientation (one right side up and the other upside down) with the sides on which the data transmitting units and data receiving units are installed facing each other, the data transmitting unit and data receiving unit of each GPS receiver faces the data receiving unit and data transmitting unit of the other. The GPS receivers paired in this manner, which constitute a GPS receiver system according to the present invention, can therefore easily exchange (send/receive) data by means of infrared beams without being electrically connected.
As each GPS receiver is provided with a data transmitting unit, a data receiving unit and a data processing unit in the foregoing manner, the GPS satellite data received by one GPS receiver can be transmitted to the other GPS receiver, and each data processing unit can process the satellite data acquired by both GPS receivers to acquire not only positioning information but also azimuth information.
Owing to the use of the infrared communications system, moreover, the two GPS receivers are easier to handle because they do not need to be interconnected by a cable.
The above and other objects and features of the invention will become apparent from the following description made with reference to the drawings.